Container image acquisition device and image acquisition method, and container inspection device and inspection method using the same

Abstract

To acquire an image for examination in which the brightness difference is sufficiently generated between an examination target and the other part in a container by suppressing influence of water drops in the container.SOLUTION: A first illumination light in the wavelength range of near infrared light and a second illumination light in the wavelength range of visible light are applied to a target region TA including an examination target 3 with a high shielding property for the visible light. After that, a first image of a target region TA in the wavelength range of the first illumination light having passed through a container 2 and a second image of a target region TA in the wavelength range of the second illumination light having passed through the container 2 are taken, and an image of the difference of the brightness between the first image and the second image is generated as an image for examination.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for acquiring images for inspecting a container having an inspection target such as a light-shielding marking provided on a light-transmitting portion that is transmissive to visible light. [Background technology]

[0002] As a method for inspecting character strings or the like on the surface of a transparent or translucent resin container, there is known an inspection method for inspecting a mold number engraved as a raised or recessed pattern on a PET (abbreviation for polyethylene terephthalate; the same applies below) resin preform, in which the preform is illuminated from behind, an image is taken of the preform observed from the front side, and the appropriateness of the engraved portion is inspected based on the obtained image (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-150072 Summary of the Invention [Problem to be solved by the invention]

[0004] When the inspection method of Patent Document 1 is applied to inspecting a container filled with liquid, illumination light incident from the back side of the container passes through the inside of the container, exits from the front side, and enters the camera. As a result, water droplets or bubbles (hereinafter sometimes referred to as water droplets, etc.) adhering to the inner wall of the container appear as dark areas in the image, which may degrade the detection accuracy of inspection objects such as markings.

[0005] Therefore, the present invention aims to provide an image acquisition device and method for acquiring an inspection image that suppresses the influence of water droplets and the like inside the container and produces a sufficient contrast between the brightness of the object to be inspected and other parts, as well as a container inspection device and method that can be used to improve inspection accuracy. [Means for solving the problem]

[0006] An image acquisition device according to one embodiment of the present invention is an image acquisition device that acquires an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the container having a light-transmitting section that is transmissive to visible light and has a light-blocking property to the visible light higher than the light-transmitting section, and the image acquisition device includes an illumination means that can irradiate a target area including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light, an imaging means that captures a first image of the target area in the wavelength range of the first illumination light that has passed through the container, and a second image of the target area in the wavelength range of the second illumination light that has passed through the container, and an image processing means that generates an image of the difference in brightness between the first image and the second image as the inspection image.

[0007] An image acquisition method according to one embodiment of the present invention is an image acquisition method for acquiring an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the container having a translucent section that is translucent to visible light and has a light-blocking property to the visible light higher than the translucent section, the method including the steps of irradiating a target area including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light, capturing a first image of the target area in the wavelength range of the first illumination light that has passed through the container, and a second image of the target area in the wavelength range of the second illumination light that has passed through the container, and generating an image of the difference in brightness between the first image and the second image as the inspection image.

[0008] A container inspection device according to one aspect of the present invention includes the image acquisition device according to the above aspect and a discrimination means for discriminating whether the inspection object is good or bad based on the contrast in the inspection image generated by the image processing means. Also, a container inspection method according to one aspect of the present invention includes a step of acquiring an inspection image by the image acquisition method according to the above aspect and a step of discriminating whether the inspection object is good or bad based on the contrast in the acquired inspection image. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an example of a basic configuration of a container inspection device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing an example of the configuration of an illumination device and an imaging device. [Figure 3] FIG. 10 is a diagram showing another example of the configuration of the lighting device and the imaging device. [Figure 4] FIG. 10 is a diagram showing yet another example of the configuration of the lighting device and the imaging device. [Figure 5] FIG. 4 is a diagram showing an example of the spectral sensitivity characteristics of a camera that can be used in the examples of FIGS. 2 and 3. [Figure 6] FIG. 5 is a diagram showing an example of the spectral sensitivity characteristics of a camera that can be used in the example of FIG. 4. [Figure 7] FIG. 4 is a diagram showing an example of a first image. [Figure 8] FIG. 10 is a diagram showing an example of a second image. [Figure 9] 9 is a diagram showing a difference image between the first image in FIG. 7 and the second image in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Basic configuration] First, the basic configuration of a container inspection device according to one embodiment of the present invention will be described. FIG. 1 shows an example of the basic configuration of the inspection device 1. The inspection device 1 is configured to inspect a PET bottle 2, an example of a container. The bottle 2 has a print unit 3 slightly below a support ring 2a, as an example of an inspection target. The bottle 2 is filled with a beverage, an example of a liquid. The top opening of the bottle 2 is sealed with a cap 4. The print unit 3 is located slightly above the liquid level L of the contents. Water droplets from the beverage may adhere to the inner wall of the bottle 2. FIG. 1 shows a water droplet D adhering behind a portion of the print unit 3. Note that FIG. 1 shows the number string "123" printed on the print unit 3, but this is just an example. The print unit 3 is formed by printing information such as the manufacturing date when the bottle was filled with liquid and sealed using an inkjet printer, as an example. However, the content of the print unit 3 and its formation method may be modified as appropriate.

[0011] The base material of bottle 2 is a translucent portion that is translucent to visible light. Translucency is a concept that includes both transparency and translucency. Printed portion 3 has a higher light-blocking property to visible light than the base material portion of bottle 2 (transparent or translucent portion) that serves as the translucent portion. Inspection device 1 utilizes the visible light-blocking property of printed portion 3 and the translucency to near-infrared light to obtain an inspection image that ensures sufficient contrast between printed portion 3 and other portions while suppressing the effects of water droplets, etc., and is intended to use the obtained inspection image to inspect the quality of printed portion 3 with high precision.

[0012] That is, for this purpose, the printed portion 3 is provided so that it can be clearly distinguished from the base material of the bottle 2 in the visible light wavelength range. Therefore, if the base material of the bottle 2 is a light-transmitting portion that transmits light in the visible light wavelength range, the printed portion 3 is formed to have a higher light-blocking property than the base material. Meanwhile, near-infrared light passes through not only the base material of the bottle 2 but also the printed portion 3. Therefore, by capturing a first image in the near-infrared wavelength range of a predetermined area including the printed portion 3 of the bottle 2 and a second image in the visible light wavelength range of the same area, and then generating an image representing the difference between the two images as a test image, the resulting test image can produce a sufficient contrast between the printed portion 3 and other areas (including areas with water droplets, etc.). The quality of the printed portion 3 can be inspected with high accuracy by comparing the printed portion 3 identified in the test image with a normal printed portion 3, for example.

[0013] The inspection device 1 includes an image acquisition device 10 for acquiring the above-described inspection image. The image acquisition device 10 includes an illumination device 11 as an example of illumination means for illuminating the bottle 2, and an imaging device 12 as an example of imaging means for capturing an image of the bottle 2. The illumination device 11 and the imaging device 12 can be configured as appropriate. Examples of these will be described later. In FIG. 1, the illumination device 11 is depicted as illuminating the bottle 2 from the side of the printing unit 3, and the imaging device 12 as capturing an image of the bottle 2 from the opposite side. However, this is a modified illustration to facilitate understanding and does not represent the actual arrangement. In an actual inspection, the inspection target, such as the printing unit 3, faces the imaging device 12, and the illumination device 11 is positioned to illuminate the bottle 2 from the opposite side.

[0014] The lighting device 11 is capable of irradiating a target area TA including the printed portion 3 of the bottle 2 with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light. As described above, the base portion of the bottle 2 is translucent to the second illumination light, and the printed portion 3 has a higher light-blocking property to the second illumination light than the base portion of the bottle 2. On the other hand, both the transparent portion of the bottle 2 and the printed portion 3 are translucent to the first illumination light.

[0015] In FIG. 1, the lighting device 11 is depicted as illuminating the printed area 3 and its vicinity, but the lighting range may be changed as appropriate as long as it can illuminate the target area TA, which is set to include at least the printed area 3, with an illumination intensity suitable for inspection. For example, the entire bottle 2 may be illuminated, or only a portion of the bottle 2 may be illuminated. Illumination by the lighting device 11 refers to irradiating the target area TA of the bottle 2 with illumination light so as to obtain the contrast required for inspection. The illumination light irradiated onto the bottle 2 with this intention is only the illumination light from the lighting device 11; no other illumination light is irradiated onto the bottle 2. However, this does not exclude the presence of illumination light or natural light in the environment in which the bottle 2 is placed.

[0016] The imaging device 12 includes at least one camera 13. The camera 13 photoelectrically converts an optical image of the target area TA of the bottle 2 using an imaging element 14, such as a CCD or CMOS, to generate an electronic image and output an image signal corresponding to the electronic image. The camera 13 is arranged to direct illumination light passing through the bottle 2 to the imaging element 14. The imaging range of the camera 13 is set so that it can capture an image of the target area TA that includes at least the printed portion 3. The images captured by the camera 13 are two types: a first image of the target area TA in the wavelength range of the first illumination light passing through the bottle 2, and a second image of the target area TA in the wavelength range of the second illumination light passing through the bottle 2. The camera 13 may be controlled to capture an image of a range wider than the target area TA, extract an image corresponding to the target area TA from the obtained image, and output an image signal for the target area TA.

[0017] [Configuration example of lighting device and imaging device] Next, several examples of the configuration of the lighting device 11 and the imaging device 12 will be described with reference to Figures 2 to 4. Note that in Figures 2 to 4, the lighting device 11 and the imaging device 12 are appropriately distinguished by adding suffixes A, B, etc., but the basic configuration in all examples is the same as that described in Figure 1.

[0018] (First configuration example) FIG. 2 shows a first configuration example. In the example of FIG. 2, an illumination device 11A and an imaging device 12A are configured to inspect bottles 2 moving in a conveying direction F along a conveying path CP of a conveying device 5. The illumination device 11A includes a first illuminator 15A that illuminates the bottles 2 at a first position P1 set on the conveying path CP, and a second illuminator 15B that illuminates the bottles 2 at a second position P2 on the conveying path CP that is different from the first position P1. The first illuminator 15A irradiates the bottles 2 with only first illumination light in the near-infrared wavelength range emitted from a light source 15a, while the second illuminator 15B irradiates the bottles 2 with only second illumination light in the visible wavelength range emitted from a light source 15b. The light sources 15a and 15b are, for example, LEDs. An LED that emits near-infrared light can be used as light source 15a, and a blue LED, green LED, white LED, or the like that emits visible light, particularly visible light in a wavelength range that is clearly separated from the wavelength of near-infrared light, can be used as light source 15b.

[0019] On the other hand, the imaging device 12A in FIG. 2 includes a first camera 13A provided corresponding to the first illuminator 15A and a second camera 13B provided corresponding to the second illuminator 15B. The first camera 13A is positioned opposite the first illuminator 15A across the bottle 2 at the first position P1. The first illumination light that has passed through the bottle 2 is incident on the first camera 13A, and the incident light is guided to the first imaging element 14A of the first camera 13A. The second camera 13B is positioned opposite the second illuminator 15B across the bottle 2 at the second position P2. The second illumination light that has passed through the bottle 2 is incident on the second camera 13B, and the incident light is guided to the second imaging element 14B of the second camera 13B. The sensitivity range of the first imaging element 14A includes at least the wavelength range of the first illumination light, i.e., the wavelength range of near-infrared light. The first camera 13A outputs an image signal corresponding to a first image of the target area TA in the wavelength range of the first illumination light. Meanwhile, the sensitivity range of the second image sensor 14B includes at least the wavelength range of the second illumination light, i.e., the wavelength range of visible light. As a result, the second camera 13B outputs an image signal corresponding to a second image of the target area TA in the wavelength range of the second illumination light.

[0020] 2, the imaging positions P1 and P2 of the first and second images are different from each other, which reduces the risk of illumination light used to capture one image being mixed into the other image. The correspondence between illuminators 15A and 15B of illumination device 11A and cameras 13A and 13B is clearly distinguished, which has the advantage of simplifying or simplifying the illumination optical system and imaging optical system.

[0021] In the example of FIG. 2, the wavelength ranges of the illumination light emitted by illuminators 15A and 15B are differentiated. Therefore, the sensitivity ranges of image capture elements 14A and 14B of cameras 13A and 13B may be set equal to each other so as to include both the near-infrared wavelength range and the visible wavelength range. A commonly available camera, for example, has sensitivity in the wavelength range of 400 nm to 1000 nm and has a spectral sensitivity characteristic that peaks at a wavelength of approximately 550 nm, as shown in FIG. 5 . By using such cameras as cameras 13A and 13B in combination with illuminators 15A and 15B, it is possible to capture a first image using only first illumination light in the near-infrared wavelength range with first camera 13A, and a second image using only second illumination light in the visible wavelength range with second camera 13B. When using a camera with the spectral sensitivity characteristics shown in Fig. 5, the wavelength range of the first illumination light can be set to at least a range of 700 nm to 1000 nm, preferably about 850 nm, and the wavelength range of the second illumination light can be set to a range of 400 nm to 650 nm. However, these wavelength ranges are merely examples. The wavelength ranges that are the subject of imaging by each of the first camera 13A and the second camera 13B may be set appropriately as long as a clear difference in the light-dark distribution corresponding to the difference in wavelength range can be produced.

[0022] Furthermore, if the sensitivity ranges of cameras 13A and 13B are controllable, cameras 13A and 13B may be controlled so that the sensitivity range of first camera 13A is set to the wavelength range of the first illumination light, and the sensitivity range of second camera 13B is set to the wavelength range of the second illumination light. For example, such settings are possible when using cameras that can simultaneously or selectively capture images in the wavelength range of near-infrared light and images in the wavelength range of visible light.

[0023] In the example of Figure 2, cameras 13A and 13B do not necessarily need to be positioned opposite their paired illuminators 15A and 15B. As long as the correspondence in which the first illumination light is incident on first camera 13A and the second illumination light is incident on second camera 13B is maintained, cameras 13A and 13B may be positioned at positions other than those shown in the figure by appropriately providing optical elements such as mirrors and prisms on the optical path of the illumination light passing through bottle 2. Optical paths between illuminators 15A and 15B and first position P1 and second position P2 may also be formed using appropriate optical elements as long as they can guide the first illumination light to bottle 2 at first position P1 and the second illumination light to bottle 2 at second position P2, respectively.

[0024] (Second configuration example) FIG. 3 shows a second configuration example. The example of FIG. 3 is similar to the example of FIG. 2 in that the illumination device 11B and the imaging device 12B are configured to inspect the bottles 2 moving in the conveying direction F along the conveying path CP of the conveying device 5. However, it differs from the example of FIG. 2 in that a first image using the first illumination light and a second image using the second illumination light are captured at the same inspection position Pi on the conveying path CP. To enable capturing two types of images with different wavelength ranges at the single inspection position Pi, the illumination device 11B is provided with a single illuminator 15C aligned with the inspection position Pi. The illuminator 15C is provided with a light source 15a for the first illumination light and a light source 15b for the second illumination light, which are appropriately mixed so that both the first illumination light and the second illumination light can be applied to the bottles 2 at the inspection position Pi.

[0025] On the other hand, the imaging device 12B of FIG. 3 further includes a beam splitter 16 and first and second filters 17A and 17B in addition to the first and second cameras 13A and 13B. The first and second cameras 13A and 13B are similar to those in the example of FIG. 2. The beam splitter 16 and filters 17A and 17B are provided to select the wavelength ranges to be imaged by each imaging element 14A and 14B, so that the first imaging element 14A captures a first image in the wavelength range of the first illumination light, and the second imaging element 14B captures a second image in the wavelength range of the second illumination light. The beam splitter 16 splits the ray bundle of the illumination light (including both the first and second illumination light) that has passed through the bottle 2 at the inspection position Pi into a ray bundle traveling in a straight direction toward the first camera 13A and a ray bundle traveling in an orthogonal direction toward the second camera 13B.

[0026] First filter 17A is disposed between beam splitter 16 and first camera 13A, and passes a light beam in the wavelength range of the first illumination light that has passed through beam splitter 16 in the straight direction, while blocking passage of light beams in other wavelength ranges (including the wavelength range of the second illumination light). Second filter 17B is disposed between beam splitter 16 and second camera 13B, and passes a light beam in the wavelength range of the second illumination light that has been bent in the orthogonal direction by beam splitter 16, while blocking passage of light beams in other wavelength ranges (including the wavelength range of the first illumination light). Note that first filter 17A may be provided as an accessory or internal part of first camera 13A, and second filter 17B may be provided as an accessory or internal part of second camera 13B.

[0027] 3, only the first illumination light in the near-infrared wavelength range is directed to the image sensor 14A of the first camera 13A, and only the second illumination light in the visible wavelength range is directed to the image sensor 14B of the second camera 13B. Therefore, the first image can be captured by the first camera 13A, and the second image can be captured by the second camera 13B. Because the first image and the second image can be captured at a single inspection position Pi, there are advantages in that the space required for installing the illumination device 11B and the image sensor 12B can be reduced and the image is not affected by changes in the position (e.g., rotation) of the bottle 2 during transport.

[0028] 3, beam splitter 16 functions as an example of a splitting means, filters 17A and 17B function as an example of a filtering means, and a combination thereof functions as an example of a wavelength range selecting means. However, instead of a combination thereof, an optical element such as a spectral prism capable of separating near-infrared light and visible light may be used as the spectral means, and the first illumination light separated by the spectral means may be directed to first image sensor 14A of first camera 13A, and the second illumination light may be directed to second image sensor 14B of second camera 13B. In that case, filters 17A and 17B may be omitted.

[0029] 3, the positional relationship between the beam splitter 16, the cameras 13A and 13B, and the filters 17A and 17B is not limited to the illustrated example and can be changed as appropriate as long as the relationship is maintained in which the illumination light split in one direction by the beam splitter 16 enters the first camera 13A via the first filter 17A, and the illumination light split in a different direction by the beam splitter 16 enters the second camera 13B via the second filter 17B. Optical elements such as mirrors and prisms may be provided on the optical path of the illumination light between the beam splitter 16 and the cameras 13A and 13B as appropriate. The optical paths between the illumination device 11B and the inspection position Pi and between the inspection position Pi and the beam splitter 16 can also be changed as appropriate as long as the illumination light can be directed to the bottle 2 at the inspection position Pi and the illumination light that has passed through the bottle 2 can be directed to the beam splitter 16.

[0030] If the sensitivity ranges of cameras 13A and 13B are controllable, cameras 13A and 13B may be controlled so that the sensitivity range of first camera 13A is set to the wavelength range of the first illumination light and the sensitivity range of second camera 13B is set to the wavelength range of the second illumination light. For example, such a configuration can be achieved by using cameras that can simultaneously or selectively capture images in the near-infrared wavelength range and images in the visible wavelength range. In this case, even if filters 17A and 17B are omitted, it is possible to capture the first image with first camera 13A and the second image with second camera 13B. In this configuration, the combination of beam splitter 16 and sensitivity control of cameras 13A and 13B functions as an example of a wavelength range selection means.

[0031] (Third configuration example) Fig. 4 shows a third configuration example. The example of Fig. 4 is similar to the example of Fig. 3 in that an image using the first illumination light and an image using the second illumination light are acquired at the same inspection position Pi on the transport path CP, and is also similar to the example of Fig. 3 in that the illumination device 11B used therefor uses a single illuminator 15C. However, it differs from the example of Fig. 3 in that a single camera 13C is used as the imaging device 12C.

[0032] 2 and 3, camera 13C includes a light-splitting prism 18 therein. Light-splitting prism 18 splits illumination light (including first and second illumination light) incident on camera 13C into first and second illumination light, and guides the split first and second illumination light to image sensors 14A and 14B, which are disposed in different directions. For example, light-splitting prism 18 splits the first illumination light in a straight direction and guides it to first image sensor 14A, and splits the second illumination light in an oblique direction and guides it to second image sensor 14B. Therefore, the light-splitting prism functions as an example of a light-splitting means. The spectral prism 18 also functions as an example of a wavelength range selection means for selecting the wavelength range to be imaged by each of the image capture elements 14A and 14B, so that the first image in the wavelength range of the first illumination light is captured by the first image capture element 14A, and the second image in the wavelength range of the second illumination light is captured by the second image capture element 14B.

[0033] By using the spectral prism 18 to guide only illumination light in the wavelength range of the object to be imaged to the image sensors 14A and 14B, it is possible to extract an image signal corresponding to a first image captured by first illumination light in the wavelength range of near-infrared light from the first image sensor 14A, and an image signal corresponding to a second image captured by second illumination light in the wavelength range of visible light from the second image sensor 14B.

[0034] 4, the first and second images can be captured at a single inspection position Pi, which has the advantage of reducing the space required for installing the illumination device 11B and the imaging device 12C and eliminating the effect of changes in the bottle 2's position (e.g., rotation) during transport. Furthermore, the imaging ranges of the imaging elements 14A and 14B built into a single camera 13C typically closely match. Therefore, there is no risk of misalignment of the target area TA between the first and second images, eliminating the need for alignment during image processing.

[0035] Cameras like camera 13C are commercially available, each configured to separate and direct a light beam in the wavelength range of an object to be imaged, using an image sensor whose sensitivity range is set to the near-infrared wavelength range and an image sensor whose sensitivity range is set to the visible wavelength range. The spectral sensitivity characteristics of an example are shown in FIG. 6. Using this type of camera, the third configuration example can be realized. There are also image sensors that stack a photoelectric conversion layer sensitive to the near-infrared wavelength range and a photoelectric conversion layer sensitive to the visible wavelength range on a single image sensor substrate, and control the charge extraction operation from these photoelectric conversion layers to simultaneously or selectively capture images in the near-infrared wavelength range and images in the visible wavelength range. When using such an image sensor, it is possible to control its imaging operation so that the single image sensor functions as either the first or second image sensor. When using such an image sensor, the spectral prism 18 can be further omitted, and the wavelength range selection means can be realized by controlling the sensitivity of the single image sensor.

[0036] (Variation) In the examples shown in FIGS. 3 and 4, the first and second images are captured simultaneously by imaging device 12B or imaging device 12C. However, if the time required for one capture is sufficiently short in consideration of the field of view of camera 13 and the transport speed of bottle 2, the first and second images may be captured alternately (in any order). For example, the first and second images can be captured by alternately emitting the first and second illumination lights from illumination device 11B and capturing images synchronized with the emission timing using a single camera 13 having a sensitivity range from visible light to near-infrared light. Alternatively, the first and second images can be captured by simultaneously irradiating illumination device 11B with the first and second illumination lights and switching the wavelength range of the illumination light incident on camera 13 between the wavelength range of the first illumination light and the wavelength range of the second illumination light, or by switching the sensitivity range of image sensor 14 of camera 13 between the wavelength range of near-infrared light and the wavelength range of visible light.

[0037] 2 to 4, the bottle 2 being transported is the subject of the inspection, but a stationary bottle may also be the subject of the inspection. If the orientation of the inspection object, such as the printing unit 3, is uncertain, the bottle 2 may be rotated about its center line, and the image of the bottle 2 may be captured by the camera 13 in time with the inspection object, such as the printing unit 3, being advanced toward the lighting device 11 and camera 13. The lighting device 11 may be constantly lit, or may be controlled to turn on and off in synchronization with the imaging operation of the camera 13.

[0038] [Control system] Returning to Figure 1, the control system of the inspection device 1 will now be described. The inspection device 1 is provided with a processing unit 20 in order to inspect the print unit 3 based on the image captured by the camera 13. The processing unit 20 is configured, for example, as a computer unit including a CPU and an internal storage device required for its operation. The processing unit 20 is provided with an image processing unit 21 and an inspection unit 22. The image processing unit 21 and the inspection unit 22 may be provided as logical devices realized by combining, for example, the hardware of the processing unit 20 with a computer program as software, or may be provided as physical devices combining logic circuits such as an LSI.

[0039] The image processing unit 21 receives the image signals of the first and second images output from the camera 13 and performs image processing to generate an inspection image to be used in the inspection by the inspection unit 22. The image processing performed by the image processing unit 21 includes processing to generate an inspection image that is a difference in brightness between the first and second images. That is, the image processing unit 21 calculates the difference in brightness between each pixel in the first image and each pixel in the second image for each pixel, thereby generating a difference image with a brightness distribution corresponding to the difference in brightness between the two images as the inspection image. By performing such processing, the image processing unit 21 functions as an example of an image processing means. In addition, the image processing unit 21 may perform various other image processing suitable for generating an inspection image that ensures a brightness difference between the printing unit 3 and other parts. For example, the image processing unit 21 may perform correction processing for image brightness, contrast, etc.

[0040] The inspection unit 22 receives an image signal corresponding to the test image processed by the image processing unit 21 and determines whether the printed part 3 is good or bad according to a predetermined algorithm. This process is, for example, a process of determining whether a part with a specific brightness corresponding to the printed part 3 appears in the test image. By performing this process, the inspection unit 22 functions as an example of a determination means. Note that the algorithm for determining whether the printed part 3 is good or bad may be configured appropriately as long as it utilizes the difference in brightness in the test image. For example, the inspection unit 22 may binarize the test image to extract the printed part 3 as a bright part, and then compare the obtained image of the printed part 3 with an image of the printed part 3 of a good product to determine whether the printed part 3 is good or bad.

[0041] As means for outputting the inspection results in the inspection section 22, a monitor 23 for displaying the inspection results, a storage device 24 for storing the inspection results, or the like may be appropriately connected to the processing unit 20. A printer may also be connected as output means. Furthermore, various input means such as a keyboard or pointing device may be connected to the processing unit 20 so that the operator of the inspection device 1 can input appropriate instructions. The input means are not shown in FIG. 1.

[0042] The image acquisition device 10 configured as described above makes use of the visible light blocking properties and near-infrared light transmissivity of the printed part 3 to obtain an inspection image that ensures sufficient contrast between the printed part 3 and other parts while suppressing the effects of water droplets, etc. Furthermore, the inspection device 1 can use the inspection image to accurately inspect the quality of the printed part 3.

[0043] Examples of images of the target area TA acquired using the image acquisition device 10 described above are shown in Figures 7 to 9. Figure 7 is an example of a first image of the target area TA of the bottle 2 captured under specified conditions, Figure 8 is an example of a second image of the same target area TA captured under the same conditions, and Figure 9 is an image showing the difference between the images of Figures 7 and 8. In the first image of Figure 7, near-infrared light is not visible because it passes through the printed area (the area where "20.05.09" can be read in Figures 8 and 9). Water droplets adhering to the printed area appear as relatively dark areas due to scattering of near-infrared light. On the other hand, in the second image of Figure 8, the printed area appears as a dark area, and the other areas have a light-dark distribution similar to that of the first image. In the image of Figure 9, it can be seen that the shadow of the bottle, water droplets, etc. are all canceled out, leaving only the printed area bright.

[0044] Since the liquid filled in the bottle is nearly black, the second image taken with visible light (Fig. 8) appears dark because the illumination light is attenuated by the liquid inside the bottle, whereas the first image taken with near-infrared light (Fig. 7) appears brighter because near-infrared light has a relatively higher transmittance than visible light. In the image in Fig. 9, the liquid part remains somewhat bright due to the difference in brightness of the liquid part, but this does not hinder the inspection of the printed part.

[0045] The present invention is not limited to the above-described embodiments and may be embodied in embodiments with appropriate modifications or alterations. For example, the container to be inspected is not limited to a bottle made of PET resin, and the present invention can be applied to any container that is translucent to both near-infrared light and visible light. For example, the present invention may be applied to a container made of polypropylene resin or polyethylene resin. The inspection object is not limited to the printed portion, and any object that has a higher light-blocking property in the visible light wavelength range compared to the translucent portion of the container may be set as the inspection object. The translucent portion may be at least a part of the container, and the inspection object may be provided in that translucent portion.

[0046] Various aspects of the present invention derived from the above-described embodiments and modifications will be described below. In the following description, corresponding components shown in the accompanying drawings will be written in parentheses to facilitate understanding of each aspect of the present invention, but the present invention is not limited to the illustrated forms.

[0047] An image acquisition device (10) according to one embodiment of the present invention is an image acquisition device for acquiring an inspection image for inspecting the quality of an inspection object (3) in a container (2) filled with a liquid, the container having a light-transmitting section that is transmissive to visible light and has a light-blocking property to the visible light higher than the light-transmitting section, and the image acquisition device includes: an illumination means (11; 11A; 11B) capable of irradiating a target area (TA) including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light; an imaging means (12; 12A; 12B; 12C) that captures a first image of the target area in the wavelength range of the first illumination light that has passed through the container, and a second image of the target area in the wavelength range of the second illumination light that has passed through the container; and an image processing means (21) that generates an image of the difference in brightness between the first image and the second image as the inspection image.

[0048] An image acquisition method according to one embodiment of the present invention is an image acquisition method for acquiring an inspection image for inspecting the quality of an inspection object (3) in a container (2) filled with a liquid, the container (2) having a transparent portion that is transparent to visible light and has a light-blocking property to the visible light higher than the transparent portion, the method including the steps of irradiating a target area (TA) including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light, capturing a first image of the target area in the wavelength range of the first illumination light that has passed through the container, and a second image of the target area in the wavelength range of the second illumination light that has passed through the container, and generating an image of the difference in brightness between the first image and the second image as the inspection image.

[0049] A container inspection device (1) according to one aspect of the present invention includes the image acquisition device (10) according to the above aspect and a discrimination means (22) that discriminates whether the inspection object is good or bad based on the contrast in the inspection image generated by the image processing means (21). Also, a container inspection method according to one aspect of the present invention includes the steps of acquiring an inspection image by the image acquisition method according to the above aspect and discriminating whether the inspection object is good or bad based on the contrast in the acquired inspection image.

[0050] In the above embodiment, the first illumination light in the near-infrared wavelength range passes through not only the translucent portion of the container but also the inspection object, so the inspection object does not appear as a dark area in the first image. On the other hand, the second illumination light in the visible wavelength range passes through the translucent portion of the container and is blocked by the inspection object, so the inspection object appears as a distinct dark area. Water droplets on the container, etc., appear with a difference in brightness between the first and second images depending on the transmittance and degree of scattering in the near-infrared and visible wavelength ranges, respectively. Therefore, in the inspection image, which is an image of the difference between the first and second images, a sufficient difference in brightness can be created between the inspection object and other parts. By utilizing the difference in brightness in the inspection image, it is possible to accurately determine whether the inspection object is good or bad, thereby improving inspection accuracy.

[0051] In the above aspect, the illumination means may include a first illumination means (15A) arranged to irradiate a container at a first position (P1) on a predetermined conveying path (CP) with the first illumination light, and a second illumination means (15B) arranged to irradiate a container at a second position (P2) on the conveying path different from the first position with the second illumination light, and the imaging means may include a first camera (13A) arranged to receive the first illumination light that has passed through the container at the first position, and a second camera (13B) arranged to receive the second illumination light that has passed through the container at the second position. This allows a first image to be captured at the first position using the first illumination means and the first camera, and a second image to be captured at the second position using the second illumination means and the second camera. The container is illuminated with near-infrared light in the wavelength range and with visible light in the wavelength range at separate first and second positions, and the first and second images are also captured at separate first and second positions, thereby eliminating the risk of the illumination light at one position mixing with the illumination light at the other position and impairing the contrast between light and dark in the inspection image.

[0052] The illumination means (11B) may be configured to irradiate both the first illumination light and the second illumination light onto the container at the same inspection position (Pi), and the imaging means may include a first imaging element (14A) and a second imaging element (14B), and wavelength range selection means (16, 17A, 17B; 18) for selecting the wavelength range to be imaged by each imaging element so that the first imaging element captures the first image in the wavelength range of the first illumination light and the second imaging element captures the second image in the wavelength range of the second illumination light. This allows the first and second images to be captured at the same position, thereby reducing the space required for installing the illumination means and the imaging means. Capturing the first and second images at the same position can also reduce or ease the effort required for alignment when generating a difference image between the two images.

[0053] The wavelength range selecting means may include a splitting means (16) that splits the first illumination light and the second illumination light that have passed through the container at the inspection position so that they are directed toward the first imaging element and the second imaging element, respectively, and a filter means (17A, 17B) that selectively passes the split first illumination light and the second illumination light according to their wavelength ranges so that the first illumination light is directed to the first imaging element and the second illumination light is directed to the second imaging element. According to this, the combination of the splitting means and the filter means can select the wavelength ranges to be imaged by each imaging element so that a first image is captured by the first imaging element and a second image is captured by the second imaging element.

[0054] The first and second image capturing elements may be provided in different cameras, and the splitting means may be provided outside the cameras. In this case, even when a general camera having a sensitivity range spanning a wavelength range from visible light to near-infrared light is used, the first illumination light may be selectively guided to the first image capturing element and the second illumination light may be selectively guided to the second image capturing element, thereby making it possible to capture the first image and the second image separately.

[0055] The wavelength range selecting means may include a spectroscopic means (18) that splits the first illumination light and the second illumination light that have passed through the container at the inspection position according to their wavelength ranges so that the first illumination light is directed toward the first image capturing element and the second illumination light is directed toward the second image capturing element. In this way, the first illumination light and the second illumination light are split using the spectroscopic means, so that the first illumination light is selectively directed to the first image capturing element and the second illumination light is selectively directed to the second image capturing element, and the first image and the second image can be captured separately.

[0056] The spectroscopic means, the first image capturing element, and the second image capturing element may be provided in the same camera (13C). This allows the first image and the second image to be captured using a single camera. This further reduces the space required for installing the image capturing means.

[0057] The target area (TA) may be set to include an inspection target provided at a position above the liquid level in the container, thereby suppressing the influence of water droplets or the like adhering above the liquid level and enabling the acquisition of an inspection image with sufficient contrast between the inspection target and other areas. [Explanation of symbols]

[0058] 1. Inspection equipment 2 bottles (containers) 3 Printing section (inspection target) 10 Image acquisition device 11, 11A, 11B Lighting device (lighting means) 12, 12A, 12B, 12C Imaging device (imaging means) 13 Camera 13A Camera 1 13B Second Camera 13C Camera 14 Image sensor 14A First image sensor 14B Second image sensor 15A 1st illuminator (1st lighting means) 15B Second illuminator (second illumination means) 15C illuminator 16 Beam splitter (wavelength range selection means, splitting means) 17A, 17B Filter (wavelength range selection means, filter means) 18 Spectroscopic prism (wavelength range selection means, spectroscopic means) 20 Processing Unit 21 Image processing unit (image processing means) 22 Inspection unit (discrimination means) CP transport route P1 1st position P2 2nd position Pi inspection position TA Inspection Area

Claims

1. An image acquisition device for acquiring an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the image acquisition device comprising: a light-transmitting section that transmits visible light; and an inspection object that has a light-blocking property against the visible light higher than the light-transmitting section; an illumination unit capable of irradiating a target area including the inspection object with first illumination light in a wavelength range of near-infrared light and second illumination light in the wavelength range of visible light; an imaging means for capturing a first image of the target area in a wavelength range of the first illumination light that has passed through the container, and a second image of the target area in a wavelength range of the second illumination light that has passed through the container; an image processing means for generating an image of a difference in brightness between the first image and the second image as the inspection image; 1. An image acquisition device for inspecting a container, comprising:

2. the illumination means includes a first illumination means provided to irradiate a container at a first position on a predetermined transport path with the first illumination light, and a second illumination means provided to irradiate a container at a second position on the transport path that is different from the first position with the second illumination light, The image acquisition device described in claim 1, wherein the imaging means comprises a first camera arranged to receive first illumination light that has passed through the container at the first position, and a second camera arranged to receive second illumination light that has passed through the container at the second position.

3. the illumination means is configured to be able to irradiate both the first illumination light and the second illumination light onto the container at the same inspection position; 2. The image acquisition device according to claim 1, wherein the imaging means comprises a first imaging element and a second imaging element, and a wavelength range selection means for selecting a wavelength range to be imaged by each imaging element so that the first imaging element captures the first image in the wavelength range of the first illumination light and the second imaging element captures the second image in the wavelength range of the second illumination light.

4. the wavelength range selection means includes a splitting means for splitting the first illumination light and the second illumination light that have passed through the container at the inspection position so that the first illumination light and the second illumination light are directed toward the first image capture element and the second image capture element, respectively; 4. The image acquisition device according to claim 3, further comprising: a filter means for selectively passing the split first illumination light and the split second illumination light according to wavelength ranges, so that the first illumination light is directed to the first image sensor and the second illumination light is directed to the second image sensor.

5. 5. The image acquisition device according to claim 4, wherein the first image pickup element and the second image pickup element are provided in different cameras, and the dividing means is provided outside the cameras.

6. 4. The image acquisition device according to claim 3, wherein the wavelength range selection means includes a spectroscopic means that disperses the first illumination light and the second illumination light that have passed through the container at the inspection position according to wavelength ranges so that the first illumination light is directed toward the first image sensor and the second illumination light is directed toward the second image sensor.

7. The image acquisition device according to claim 6 , wherein the spectroscopic means, the first image sensor, and the second image sensor are provided in the same camera.

8. An image acquisition device according to any one of claims 1 to 7, wherein the target area is set to include an inspection object positioned above the liquid level of the liquid in the container.

9. An image acquisition device according to any one of claims 1 to 8; and a discrimination means for discriminating whether the inspection object is good or bad based on the difference in brightness in the inspection image generated by the image processing means.

10. An image acquisition method for acquiring an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the inspection object being provided in a light-transmitting portion that is transmissive to visible light and has a light-blocking property against the visible light higher than that of the light-transmitting portion, the method comprising: a step of irradiating a target area including the inspection object with first illumination light in a wavelength range of near-infrared light and second illumination light in the wavelength range of visible light; capturing a first image of the target area in a wavelength range of the first illumination light that has passed through the container and a second image of the target area in a wavelength range of the second illumination light that has passed through the container; generating an image of a difference in brightness between the first image and the second image as the test image; An image acquisition method for inspecting a container, comprising:

11. acquiring an inspection image by the image acquisition method of claim 10; and a step of determining whether the inspection object is good or bad based on the difference in brightness in the acquired inspection image.

Images